1. Field of Endeavor
The present disclosure relates to an apparatus and method for detecting failure of switching device in inverter.
2. Background
This section provides background information related to the present disclosure which is not necessarily prior art.
Generally, an inverter is a device used for motor control. FIG. 1 illustrates a schematic view illustrating an inverter according to prior art.
Referring to FIG. 1, a conventional inverter (100) for controlling a motor (200) includes a rectifying unit (110) converting an inputted 3-phase AC power source to a DC power source, a smoothing unit (120) smoothing a pulsation component of a DC voltage outputted from the rectifying unit (110) and an inverter unit (130) converting the DC voltage outputted from the smoothing unit (120) to an AC voltage and providing the AC voltage to the motor (200).
The thus-mentioned inverter (100) is such that a diode in the rectifying unit (110) is formed by a bridge coupling, the smoothing unit (120) is formed with a capacitor, and the inverter unit (130) is used by being connected with a plurality of switching elements. Recently, an IGBT (insulated Gate Bipolar Transistor) excellent in characteristics as a switching element has been widely used.
As noted from the foregoing, the inverter (100) is complicatedly comprised of a plurality of elements, such that if anything happens on the inverter (100), there is no way of visually checking the issues to make it difficult to detect a defected portion.
Particularly, a switching element in the inverter unit (100) is where the failure frequency is the highest, and in order to check the failure of the switching element, a multi-tester was conventionally employed to determine the failure by measuring each resistance of the switching element, which disadvantageously takes too many hours to check or detect the failure.
In order to solve the aforementioned problems, a failure detection device has been disclosed as shown in FIG. 2 which is a schematic circuit diagram illustrating a failure detection device in a switching element (device) according to prior art.
Referring to FIG. 2, a conventional switching element failure detection device (300) is connected to the inverter (100) to prevent an input voltage from being applied to an input terminal of the inverter (100), whereby connection to an output terminal is also disconnected to the motor (200).
As noted from the foregoing, the conventional switching element failure detection device (300) is conceived by the fact that, in a case a failure happens on an IGBT which is a switching element due to over current, a short-circuit occurs in advance in an inner circuit of the IGBT, and an open phenomenon is generated by the over current, whereby an occurrence of open phenomenon in the IGBT is detected.
That is, a gate pulse generating unit (320) sequentially applies a gate pulse to each of the IGBT elements, and determination is made that a failure has occurred to the relevant IGBT, in a case a phase voltage outputted from a relevant IGBT element is not high.
However, the conventional switching element failure detection device (300) suffers from disadvantages in that the inverter (100) and the motor (200) must be stopped to determine the failure to consume an additional time for failure detection, and a separate hardware is required for failure detection of the switching elements to increase the size of the system.
In order to solve the disadvantages, attempts have been made to realize the failure detection of the switching element by way of software. Although configuration is not shown in the inverter (100) in FIG. 1, output currents are periodically measured from a current sensor detecting an output current outputted to the motor (200), an average of the output currents is obtained, and in a case the average is zero (0), it is determined that the switching element is normal, and in a case the average is not zero, it is determined that the switching element is abnormal.
However, the abovementioned prior art also suffers from disadvantages in that it takes many hours to detect the failure, because output currents are sensed from a plurality of points of an AC current (sine waveform) in a period and an average is obtained therefrom.